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Nuclear Energy Conference & Expo (NECX)
September 8–11, 2025
Atlanta, GA|Atlanta Marriott Marquis
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Deep geologic repository progress—2025 Update
Editor's note: This article has was originally published in November 2023. It has been updated with new information as of June 2025.
Outside my office, there is a display case filled with rock samples from all over the world. It contains a disk of translucent, orange salt from the Waste Isolation Pilot Plant near Carlsbad, N.M.; a core of white-and-bronze gneiss from the site of the future deep geologic repository in Eurajoki, Finland; several angular chunks of fine-grained, gray claystone from the underground research laboratory at Bure, France; and a piece of coarse-grained granite from the underground research tunnel in Daejeon, South Korea.
Milan Hanus, Jean C. Ragusa
Nuclear Science and Engineering | Volume 194 | Number 10 | October 2020 | Pages 873-893
Technical Paper | doi.org/10.1080/00295639.2020.1767436
Articles are hosted by Taylor and Francis Online.
This work is motivated by the need to solve realistic problems with complex energy, space, and angle dependence, which requires parallel multigroup transport sweeps combined with efficient acceleration of the thermal upscattering. We present various iterative schemes based on the two-grid (TG) diffusion synthetic acceleration (DSA) method. In its original form, the TG method is used with the Gauss-Seidel iterative scheme over energy groups, which makes it impractical for parallel computation. We therefore formulate a Jacobi-style version. Furthermore, we propose a new scheme that reduces the overall number of transport sweeps by removing the need to fully converge the within-group iterations before the TG step. This becomes possible by adding an additional within-group DSA solve after each transport sweep. Fourier analyses are carried out to ascertain the effectiveness of the proposed scheme, with further corroboration from massively parallel numerical results from practical problem calculations. We discuss several implementation strategies of the new scheme, paying particular attention to the consequences on the overall efficiency of adding additional diffusion solves with a relatively low number of degrees of freedom per process.